You will notice that //CALL apoc.load.csv($url) YIELD map AS row RETURN row is commented out. While that is supposed to work. One of the files at the URL I was calling was throwing an error, so at this point I had to use LOAD CSV instead.

EXPLANATION

The first part of the code

LOAD CSV WITH HEADERS FROM "https://docs.google.com/spreadsheets/d/1sFcY7LFBCGXSFG336UPoOf72BBv3bmv_AVaYLxwiV4A/export?format=csv&id=1sFcY7LFBCGXSFG336UPoOf72BBv3bmv_AVaYLxwiV4A&gid=1318941318" AS row1
WITH CASE
WHEN NOT row1.Year IS NULL THEN collect(row1.URL)
END AS fileURLs
UNWIND fileURLs as fileURL

loads the file URLs from the shared Google Sheet. The WITH clause is included to "ignore" rows where the file URL has not been verified. All that satisfy are put into a collection and then using the UNWIND passed in to the next batch of code contained within the apoc.periodic.iterate function. The code within apoc.periodic.iterate load the data for each url and add it to the graph using MERGE.